The invention relates to platinum metal cermet electrodes for the electrochemical reduction of O2, the ceramic component of which contains stabilized ZrO2 as its main constituent.
The electrochemical reduction of oxygen plays a role in gas sensors for the analysis of gas mixtures containing O2. Such gas sensors are described, for example, in German Patent Application 39 34 586 A1, German Patent Application 42 40 267 A1 and German Patent Application 198 33 087 A1. The platinum metal cermet electrodes used are printed on substrates of Y-stabilized ZrO2. The platinum metal cermet electrodes normally have a ceramic component of 40 vol.-% (the supporting structure) and a 60 vol.-% metallic component. The supporting structure is primarily made up of Y-stabilized ZrO2 which contains 10 wt.-% Y2O3 with respect to the ZrO2 component in terms of order of magnitude. The ceramic addition should ensure a certain porosity of the electrode material and it should also extend the electrochemically effective three phase limit of the actual contact surface between substrate and electrode based on the ionic conductivity of the supporting structure into areas of the electrode. The O2 pump flows obtained with the known electrodes are still not satisfactory.